Condition responsive device



Dec. 28, 1965 R. C. DU BOIS ETAL CONDITION RESPONSIVE DEVICE Filed April 29, 1963 5 Sheets-Sheet 1 INVENTORS ROBERT C. Du BOIS RANDALL GOFF EDWARD II. PLAVCAN A TORNEY Dec. 28, 1965 R. c. DU BOIS ETAL 3,225,622

CONDITION RESPONSIVE' DEVICE 5 Sheets-Sheet 2 Filed April 29, 1963 FIG. 4

INVENTORS ROBERT C. DuBOIEi RANDALL GOFF BY EDWARD J. PLAVCAN TTOR NE Y 28, 1965 R. c. DU BOIS ETAL 3,225,622

CONDITION RESPONSIVE DEVI GE Filed April 29, 1963 5 Sheets-Sheet 5 INVENTORS ROBERT C. Du BOIS RANDALL GOFF EDWARD I PLAVCAN 4/ jaw;

ATTORNEY United States Patent 3,225,622 CONDITION RESPONSIVE DEVICE Robert C. Du Bois, Fairfield, Randall Goff, Weston, and

Edward .I. Plavcan, Stratford, Conn, assignors, by

mesne assignments, to Dresser Industries, Inc., Dallas,

Tex., a corporation of Delaware Filed Apr. 29, 1963, Ser. No. 276,647 18 Claims. (Ci. 74-522) This invention relates to a condition responsive device and more particularly to such a device adapted to actuate multi-condition control means such as an electrical switch in response to changes in a condition such as pressure or temperature.

It is an object of this invention to provide a condition responsive device having novel and improved means for actuating multicondition control means in response to changes in a sensed condition.

It is a further object of tlns invention to provide a condition responsive device for actuating control means and including novel and improved adjustable means for preselecting the values of the sensed condition at which the control means will be actuated.

Included within the foregoing objects is the object of providing a pressure or temperature responsive device for actuating an electrical switch when the pressure or temperature is at either two values and including novel and improved means for setting the values of pressure or temperature at which the switch will be actuated.

Other objects will be in part obvious, and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application of which will be indicated in the appended claims.

In the drawings:

FIG. 1' is a front elevational view of a pressure responsive switch incorporating the present invention with a por tion of the switch housing being cut away to reveal internal elements;

FIG. 2 is a cross-sectional view of the switch of FIG.

FIG. 3 is an elevational view of a portion of the device of FIG. 1;

FIG. 4 is an enlarged, fragmentary cross-sectional view substantially along the line 4-4 of FIG. 3;

FIG. 5 is an enlarged, fragmentary cross-sectional view substantially along the line 5-5 of FIG. 1;

FIG. 6 is an enlarged, fragmentary elevational view substantially along the line 6-6 of FIG. 2;

FIG. 7 is a fragmentary elevational view of a portion of the elements of FIG. 3, illustrating the position of the elements in a different condition of the device; and

FIG. 8 is an elevational view of the portion of the mechanism of FIG. 3 shown in reverse orientation to illustrate particular structure of this element.

With reference to the drawings, a preferred embodiment of the invention is depicted therein in the form of a pressure responsive electrical switch adapted to provide a change in condition of external control means in response to an increase or reduction of the pressure being sensed to preselected values. While the invention will be described in terms of this specific instrument and in connection with a specific condition to be sensed and specific control means to be actuated, it will be understood that the invention is not limited in its application to this particular device or manner of use.

3,225,622 Patented Dec. 28, 1965 With reference to FIG. 1, an exemplary pressure responsive switch embodying the present invention comprises a casing 10 which as shown in FIG. 2 includes a generally cupped shaped housing 11. Closing the front open end of the housing 11 is a transparent glass plate 12. The glass 12 is held on the housing 11 by a bezel or ring 13. Disposed within the housing 11 is a back plate 14 which supports a portion of the switch mechanism. The back plate 14 is secured to the rear wall of the housing 11 and has mounted integrally thereon a fitting or socket 15 which extends externally of the housing 11. The outer end of the socket 15 is adapted to be connected to a source of fluid pressure. As shown in FIGS. 1 and 3, one end of a conventional Bourdon tube 16 is connected to the socket 15 to fix the end of the tube relative to the socket and to connect the interior of the tube to an internal passage (not shown) in the socket which is adapted to be connected to fluid pressure.

The free end of the tube 16 is pivotally connected to one end of a link 17. The other end of the link is pivotally connected to one end of a beam assembly 18, as most clearly shown in FIGS. 3, 7 and 8. The beam assembly in FIG. 8 is shown from the reverse side of that viewed in FIGS. 3 and 7. As can be seen, the beam comprises a generally elongated sheet metal member 19, the opposite end of which are laterally spaced relative to each other within the general plane of the beam. As shown in FIG. 5, the end of the beam opposite the link 17 is pivotally connected to the base portion 21 of a switch bracket assembly 22. As most clearly shown in FIG. 5, the base member 21 is a generally U-shaped bracket having depending legs formed with apertures receiving a fixed shaft 23 which is mounted on and extends from the back plate 14. The pivotal connection of the beam member 19 to the base 21 is provided by a pair of pin-like members 20 extending at right angles to the general plane of the member 19 and loosely received in apertures in the depending legs of the base 21. A switch bracket 24 is fixed to the base 21 and extends generally upwardly therefrom. The bracket 24 is preferably fabricated from resilient sheet metal and clampingly mounts a mercury switch 26 of conventional construction. The electrical connections for the mercury switch extend outwardly of the housing through a strain relief assembly 28 as shown in FIG. 1. As shown in FIG. 3, the switch bracket 24 has a skeletonized construction providing a pair of spaced apart sides 29 and 30. The sides 29 and 30 serve as stops or abutments which are engageable with a fixed stop 32 which is mounted on the back plate 14 and extends at right angles thereto and parallel to the switch bracket shaft 23. The stop 32 which extends between the sides 29 and 30, as will be later seen, serves a second purpose, that of supporting a front plate 34 which carries a portion of the mechanism to be described.

Referring to FIG. 8, the beam member 19 is provided with an elongated slot 36 extending longitudinally thereof from adjacent the pivotal connection to the link 17. Mounted on this portion of the member 19 are a pair of span adjustment clamps 38 and 39. As shown in FIG. 4, these clamps have a generally U-shaped cross-section and fit over the member 19, being held thereon by clamps screws 40 and 41 which extends through the slot 36. The clamp screw 40 associated with the clamp 38 has a projection which as shown in FIG. 4 extends at right angles to and away from the back plate 14 to form a pin 42. The pin 42 extends parallel to the pivotal connections at either end of the beam assembly. The position of the pin 42 may be adjusted longitudinally of the slot 36 in the beam member 19 by means of a micrometer screw 43 which as shown in FIG. 8 is threadably mounted on the clamp 39 and extends parallel to the slot 36. One end of the micrometer screw 43 bears upon the clamp 38 associated with the pin 42 whereby inward threading of the micrometer screw will cause corresponding movement of the pin 42 longitudinally of the slot 36. The clamp screw 40 7 serves to secure the pin 42 in its selected adjusted position.

Referring back to FIG. 3, the device is shown with the mercury switch in an on condition and with the Bourdon tube in a position corresponding to zero pressure. It will be seen that if the Bourdon tube internal pressure is increased, thus causing a generally counterclockwise movement of the free end of the tube, as viewed in FIG. 3, the beam assembly 18 will be pivoted in a counterclockwise direction about the pivot points 20 without effecting any movement of the switch bracket 22. Correspondingly, on a subsequent decrease in pres sure the beam assembly would merely pivot in a clockwise direction about the pivots 20 without effecting the condition of the switch 26. However, if at any point in its travel the pin 42 is restrained against counterclockwise movement about the pivots 20, subsequent movement of the outer end of the beam assembly 18 in a counterclockwise direction would cause the beam assembly to pivot about the pin 42 as a fulcrum so as to effect counterclockwise movement of the pivots 20 and a corresponding counterclockwise movement of the switch bracket 22. Correspondingly, a clockwise movement of the free end of the Bourdon tube 16 will effect clockwise movement of the switch bracket 22, provided that the pin 42 is appropriately restrained.

In this connection and as can be seen from FIG. 3, the pin 42 is engageable with a rail 44 to limit movement of the pin 42 in a counterclockwise direction about the pivots 20. The rail 44 and associated structure is best shown in FIG. 6 in which the rail and associated structure are viewed from the direction opposite that of FIG. 3. The rail 44 is fixedly mounted on an adjustable member or arms 46 which is pivotally mounted at one end on a pin 48. As best shown in FIG. 4, the pin 48 has an enlarged head 50, journaled on a front plate 34, the front plate 34 is supported in parallel relation to the back plate 14 by the support and stop member 32, as described in connection with FIG. 5. The front plate is additionally supported on the socket assembly 15, as best shown in FIG. 6, by means of slots 51 which embrace screws 52 which are threaded into projections 53 extending from the socket as best shown in FIGS. 2 and 3. As best shown in FIG. 1 and for a reason which will be hereinafter explained, the head 50 of the pin 48 is constructed. and arranged eccentrically of the axis of the pin.

Turning back to FIG. 6, the arm 46 is provided at its end opposite the pin 48 with a cam follower 55 engageable with an eccentric plate cam 56. A tension spring 47 biases the arm 46 and thus the cam follower 55 toward the' cam 56. The cam 56 is journaled on a bushing 58 carried by the front plate 34. The bushing is disposed generally concentrically of the housing 11. The cam 56 is provided with a radially extending arm 59 as most clearly shown in FIG. 1. The arm 59 carries at its outer end a pointer 68 which overlies a dial plate 61. As shown in FIG. 2, the dial plate 61 is disposed between the front plate 34 and the glass 12 and the cam 56 is disposed on the side of the front plate opposite the dial plate 61. The arm 59 extends beyond the periphery of the dial plate and is then re-directed radially inwardly of the plate to provide the pointer portion 60 which is disposed in overlying relation to the dial plate 61. The dial plate is provided with a plurality of indicia cooperating with the pointer 60 to assist in setting of the cam 56. As best shown inFIGS. 2 and 6, the dial plate 61 is mounted on the front plate 34 by means of screws 62 which are threaded in an upwardly struck portion 63 of the front plate 34.

It will be apparent that movement of the pointer 60 about the axis of the cam 56 will effect corresponding movement of the cam, which will in turn effect movement of the arm 46 carrying the rail 44. This will in turn determine the position of the Bourdon tube 16 at which the pin 42 on the beam assembly will engage the rail 44 to provide a fulcrum for the pin 42 during a decreasing pressure condition. In order to provide a fulcrum for the pin 42 during the increasing pressure condition, there is provided a rail 66 which, as shown in FIG. 6, is disposed on the opposite side of the pin 42 from the rail 44 and extends generally angularly of the rail 44 within the same general plane. The rail 66 is formed integrally with an arm 68 which is pivoted at one end on the pin 48. Also pivoted at one end on the pin 48 is an arm 70, which extends generally parallel to the arm 68 in overlying relation. The arms 68 and 70 are connected by a tension spring 62 which urges the arm 68 into engagement with a stop 74 on the arm 70. The arm 70 carries a cam follower 76 which is engageable with the periphery of an eccentric plate cam 78 mounted on the bushing 58. The cam 78 has a radially extending arm 79, provided at its outer end with a pointer portion 80 formed similarly to the pointer 60 so as to overlie the dial plate 61. The follower 76 is urged into engagement with the cam 78 by a tension spring 82 connected between the arm 78 and the front plate 34.

In the operation of the device just described, the pointers 68 and 80 are set at the desired low and high pressures, respectively, at which it is desired to actuate the switch 26. i As shown in FIG. 1, the pointers are set at the extreme low and high pressure settings of the device. However, in actual use, the pointers would normally be set at intermediate positions between these extreme positions. As will be apparent from the foregoing, the adjustment of the pointers 60 and 80 with the corresponding adjustment of the cams 56 and 78 will adjust the angularity between the rails 44 and 66. In this manner, the unrestrained movement of the pin 42 is determined, thus determining the range of movement of the Bourdon tube which is permitted without causing actuation of the switch from one condition to the other. Not only is the range of movement of the Bourdon tube determined in this manner, but also the portion of the pressure range of the device within which pressure ranges can occur without causing actuation of the switch 26. Assuming that the switch is in the on condition shown in FIG. 3 and the pin 42 is in engagement with the rail 44, an increase in pressure will cause the Bourdon tube to move in a generally counterclockwise direction, so that the pin 42 moves away from the rail 44 with the beam assembly being pivoted about the pivot 20 without causing any movement of the switch bracket 22. However, on sufiicient increase in pressure, the pin 42 will engage the rail 66, as shown in FIG. 7, and further increase in pressure will cause the beam assembly to pivot about the pin 42 to cause a generally counterclockwise movement of the pivot pin 20, as viewed in FIG. 7, about the axis of the shaft 23 mounting the switch bracket. Accordingly, the switch bracket will be pivoted in a counterclockwise direction, as viewed in FIG. 7, to place the switch in the off condition shown in that figure.

It should here be noted that it is preferred that the pins 20 be relatively loosely received in the holes in the switch bracket base 21 so that a lost motion connection is provided between the member 19 and the switch bracket base 21. Further, the holes in the base plate 21 receiving the pins 20 are located radially of the pivotal axis of the switch bracket on lines extending at right angles to the general longitudinal axis of the bracket. More specifically, the holes receiving the pins 20 are located on lines extending through the axis of the shaft 23 and at right angles to a line extending through that axis and through the Center of gravity of the switch assembly. When the switch assembly is in either of its extreme positions, the center of gravity will be on opposite sides of a vertical line drawn through the axis of the shaft 23 and hence the bracket would tend to remain in either the on or off position once it is in such position. Further, as the bracket is rotated from one position toward the other, as soon as the center of gravity passes through a vertical line extending through the axis of the shaft 23, the bracket will tend to be moved towards the other position by the force of gravity. The lost motion connection between the pins 20 and base 21 permit the switch bracket to overtravel the pins and provide somewhat of a snap action to the switch actuation. In order further to enhance this snap-like action of the switch, the pivotal connection between the beam member 19 and link 17 and between the link 17 and Bourdon tube, are preferably rather loose to provide additional lost motion in the system. It will be apparent to those skilled in the art that if desired a suitable over-toggle arrangement or other mechanism could be provided to achieve a snap action characteristic to switch actuation.

With the switch in the off position, as shown in FIG. 7, if there is a further increase in pressure, movement of the pins 20 in a downward or generally counterclockwise direction about the axis of the shaft 23, will not be permitted due to the abutment of the switch bracket on the stop 32. Accordingly, any increase in pressure will tend to cause the pin 42 on the beam assembly to be moved upwardly in a counterclockwise direction about the axis of the shaft 23. The attendant force on the rail 66 will, as is best shown in FIG. 6, cause the arm 68 to move counterclockwise, as viewed in FIG. 6, about the pin 48 and against the force of the spring 72. The arm 70 will, of course, remain in the position shown with the cam follower 76 engaged with the cam 78. This displacement of the arm 68 relative to the arm 70, as shown in broken line in FIG. 6, precludes any overstressing or damage to the parts should the pressure in the Bourdon tube exceed that set by the maximum pointer 80. As the pressure decreases, the arm 68 will resume the solid line position shown in FIG. 6, and on a further decrease in pressure, the pin 42 will move toward the rail 44 without any attendant movement of the switch bracket 22 until the pin engages the rail 44. Further decrease in pressure will cause the beam to pivot about the pin 42 until the switch bracket has been pivoted sufficiently for the center of gravity thereof to be disposed on the opposite side of a vertical line passing through the shaft 23, whereupon the switch bracket will fall into the on position shown in FIG. 3. On a further decrease in pressure, beyond the point where the pins 20 on the beam member 19 can move clockwise about the axis of the shaft 23, the pin 42 will force the arm 46 in a clockwise direction about the pin 48, as viewed in FIG. 6, and against the force of the spring 47; This will preclude any overstressing or damage to the parts due to underpressure of the device below that set by the minimum pressure pointer 60.

As discussed before, the pressures at which the switch will be actuated are determined by the settings of the cams 56 and 78, whereby the angle or spacing between the rails 44 and 66 are determined. The micrometer adjustment of the pin 42 longitudinally of the beam member 19 permits adjustment of the span between the high and low settings of the device thereby to correct any inaccuracies inherent in the manufacture of the instrument. Additionally, a zero adjust feature is provided by the eccentric head 50 of the pin 48 mounting the arms 46, 68 and 70. As will be apparent from a consideration of FIGS. 1 and 6, rotation of the head 50 will cause a displacement of the pin 48 laterally relative to the pin 42. so as to adjust the entire rail mechanism relative to the pin 42. Another advantages of the device of this invention will be apparent from a consideration of FIGS.

1 and 2. The generally annular bushing 58 which mounts the cams56 and 78 is in registry with the mercury switch 26. The dial plate 61 is provided with an opening aligned with and of greater diameter than the bushing. The inner diameter of the bushing and the location of the bushing relative to the switch bracket assemby 22 is such that the terminals of the switch 26, as well as at least a portion of the switch bracket assembly, may be viewed from externally of the device through the transparent cover glass 12. In this manner the bushing 58 not only provides the means for mounting the cams but also provides visual access to the mercury switch and bracket therefor after the switch has been assembled so that the condition and operation of the switch may be observed. Therefore, the physical as well as electrical condition of the switch may be readily checked from time to time, and the physical movement of the switch bracket assembly may also be observed from the standpoint of proper operation as well as visually determining whether the switch is on or off prior to disconnecting or connecting the power leads to the switch.

It will thus be seen that there has been provided a pressure responsive switch having novel and improved means for setting the high and low limits of switch actuation and for actuating the switch. While the devices have been described in terms of a pressure responsive switch, the same structure as heretofore described is adapted for use in a temperature responsive system. In this case, a liquid filled bulb might be connected to the Bourdon tube with the pressure of the liquid fill varying with temperature. Alternately, other types of pressure or temperature or other condition responsive elements could be substituted for the Bourdon tube 16, and control means other than a mercury switch could be substituted, all without departing from the scope of this invention.

Inasmuch as many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the language in the following claims is intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

We claim:

1. In a condition responsive device, an actuating member, yieldable pivot means mounting one end of said member, means for moving the other end of said member in one direction about said pivot means, fulcrum means spaced substantially from and engageable with said member intermediate the ends of said member for restraining movement of said member about said pivot means in response to movement of said member a predetermined amount about said pivot means in said one direction whereby upon continued movement of said other end of said actuating member in said one direction said yieldable pivot means will be moved relative to said fulcrum means, and means responsive to the movement of said yieldable pivot means.

2. A condition responsive device as described in claim 1, in which said fulcrum means includes abutment means engageable with said actuating member in response to movement of said other end of said member about said pivot means and means for adjusting the spacing of said abutment means relative to said actuating member.

3. In a condition responsive device, an actuating member, means providing a yieldable pivot at one end of said member, means connected to the other end of said member for moving the same in one direction about said yieldable pivot, a second pivot on said actuating member intermediate the ends thereof, and abutment means spaced substantially from said second pivot and engageable by the same in response to a predetermined movement of said other end of said actuating member in said one direction about said yieldable pivot so as to permit movement of said other end of member initially about said yieldable pivot and segmentially about an axis intermediate said other end and said yieldable pivot.

4. In a condition responsive device, an actuating member, means providing a yieldable pivot at one end of said member, means connected to the other end of said member for moving the same about said yieldable pivot, a pivot pin carried by and disposed intermediate the ends of said member, and abutment means on opposite sides of said pivot pin and spaced substantially therefrom, said pin being engageable with said abutment means to provide a fulcrum intermediate the ends of said actuating member in response to movement of said other end of said actuating member a predetermined angular distance about said yieldable pivot in either direction.

5. A condition responsive device as described in claim 4, in which said pivot pin is adjustable, generally toward and away from said other end thereof.

6. A condition responsive device as described in claim 4, in which said abutment means extend angularly of each other, and means mounting said abutment means for adjustment relative to each other to vary the angle therebetween.

7. A condition responsive device as described in claim 6, in which said pivot pin is mounted for selective adjustment along said actuating member and generally in a direction extending longitudinally of said abutment means.

8. In a condition responsive device, an actuating member, means providing a yieldable pivot at one end of said member, means for moving the other end of said member about said yieldable pivot, pivot means on said member intermediate its ends, restraining means engageable by said pivot means during movement of said actuating member about said yieldable pivot, said restraining means being movable toward and away from said pivot means generally in the direction of movement of said pivot means, and means for adjusting the position of said restraining means relative to said pivot means.

9. A condition responsive device as described in claim 8 in which said restraining means comprises a pair of lever arms pivotally mounted on one end for movement about a common axis, means yieldably urging said lever arms toward each other, stop means on each of said arms limiting movement thereof toward each other, and an elongated abutment on one of said lever arms engageable with said pivot means and extending generally laterally of the direction of movement of said pivot means.

10. A condition responsive device as described in claim 9 in which said restraining means further comprises a third lever arm mounted for pivotal movement about the axis of said pair of lever arms, said third lever arms including an elongated abutment extending angularly of the first-mentioned abutment on the opposite side of and being engageable by said pivot means.

11. In a condition responsive device, an actuating member, control means comprising a pivoted support member having a pivotal axis extending at right angles to the general plane of said actuating member, means pivotally connecting one end of said actuating member to said pivoted member for relative movement therebetween about an axis extending parallel to the axis of said pivoted member and spaced laterally therefrom, means for moving the other end of said actuating member about the axis of the pivotal connection between the actuating member and control means, pivot means intermediate the ends of said actuating member, abutment means for restraining said pivot means at a selected value of the condition being sensed to provide for movement of said one end of the actuating member about the axis of said pivot means in response to movement of said other end of said actuating member, thereby to pivot said control means between one position and another position.

12. In a device as described in claim 11, the center of gravity of said control means being disposed vertically above the pivotal axis of said support member and being disposed on opposite sides of the vertical line through said pivotal axis of said support memberin each of said positions.

13. In a condition responsive device, an actuating member, means providing a yieldable pivot for one end of said actuating member, means connected to the other end of said actuating member for moving the same about said yieldable pivot, a pivot pin extending parallel to the axis of said yieldable pivot, means mounting said pivot pin on said actuating member for movement in a direction extending generally between the ends thereof, means for selectively adjusting the position of said pivot pin along said actuating member including a threaded member,

and means for restraining said pivot pin in its movement about said yieldable pivot to provide a fulcrum therefor during movement of said actuating member over at least a portion of the total range of movement of said actuating member.

14. In a condition responsive device, an actuating member, means providing a yieldable pivot for one end of said actuating member, condition responsive means connected to the other end of said actuating member to move the same about said yieldable pivot, means providing a pivot member intermediate the ends of said actuating member having an axis extending parallel to the axis of said yieldable pivot, means providing a pair of adjustable abutments disposed on opposite sides of said pivot on the actuating member and in the path of movement thereof, said abutments being spaced apart, means for selectively adjusting each of said abutments relative to each other and to the pivot on the actuating member, said last mentioned means including a pair of cams, said cams being rotatably mounted for movement about a common axis, an arm extending from each of said cams and having at the end thereof pointer means, a dial plate associated with said device and having indicia cooperating with said pointer means.

15. In a condition responsive device as described in claim 14, control means responsive to movement of said yieldable pivot, said cams being mounted for rotation by an annular member disposed in registry with at least a portion of said control means, said annular member being visible from the exterior of said device whereby the condition and operation of said control means may be viewed from externally of the device.

16. In a condition responsive device as described in claim 15, said annular member being disposed adjacent said dial plate in generally underlying relation thereto, said dial plate having an opening in registry with said annular member, and a transparent cover in overlying spaced relation to said dial plate whereby the portion of the device in underlying registry with said annular member may be viewed from externally of the device.

17. In a condition responsive device, a generally cylindrical casing, a pair of cams mounted for movement about a common axis, a pair of pivoted lever means each having a cam follower engageable respectively with said pair of cams, said lever means carrying spaced apart abutment means moveable toward and away from each other in response to movement of said cams, an actuating member, means providing a yieldable pivot at one end of said actuating member, condition responsive means operatively connected to the other end of said actuating member for movement of the same about said yieldable pivot, means providing a pivot pin intermediate the ends of said actuating member, said pivot pin extending between said abutment means and being engageable therewith during movement of said actuating member about said yieldable pivot.

18. In a condition responsive device, an actuating member, yieldable pivot means mounting one end of said member, means for moving the other end of said member in one direction about said pivot means, fulcrum means intermediate the ends of said member for restraining movement thereof about said pivot means upon movement of said member a predetermined amount about said pivot means whereby upon continued movement of said other end of said actuating member in said one direction said yieldable pivot means will be moved relative to said fulcrum means, means mounting said fulcrum means for adjustment relative to said pivot means, cam means for adjusting said fulcrum means, control means responsive to movement of said yieldable pivot, andmeans mounting said cam means including an annular member disposed in registry with at least a portion of said control means to permit visual observation of the condition and operation of said portion of said control means from externally of the device.

References Cited by the Examiner UNITED STATES PATENTS 1/1937 Diehl 741 X 9/1937 Runaldue 7497 X 2/1940 Wurr 74-522 12/ 1942 Butler et a1 74522 X 12/ 1949 Branson 74522 12/1953 Markson 741 X 5/1957 Cronk 74522 FOREIGN PATENTS 5/1958 France.

15 BROUGHTON G. DURHAM, Primary Examiner.

MILTON KAUFMAN, Examiner. 

1. ION A CONDITION RESPONSIVE DEVICE, AN ACTUATIONG MEMBER, YIELDABLE PIVOT MEANS MOUNTING ONE END OF SAID MEMBER, MEANS FOR MOVING THE OTHER END OF SAID MEMBER IN ONE DIRECTION ABOUT SAID PIVOT MEANS, FULCRUM MEANS SPACED SUBSTANTIALLY FROM AND ENGAGEABLE WITH SAID MEMBER INTERMEDIATE THE ENDS OF SIAD MEMBER FOR RESTRAINING MOVEMENT OF SAID MEMBER ABOUT SAID PIVOT MEANS IN RESPONSE TO MOVEMENT OF SAID MEMBER A PREDETERMINED AMOUNT ABOUT SAID PIVOT MEANS IN SAID ONE DIRECTION WHEREBY UPON CONTINUED MOVEMENT OF SAID OTHER END OF SAID ACTUATING MEMBER ION SAID ONE DIRECTION SAID YIELDABLE PIVOT MEANS WILL BE MOVED RELATIVE TO SAID FULCRUM MEANS, AND MEAND RESPONSIVE TO THE MOVEMENT OF SAID YIELDABLEE PIVOT MEANS. 